Were polio vaccines properly tested?

After a New York Times article exposed Aaron Siri as the guy who petitioned to get a polio vaccine removed from the market, he shot back with a long tweet claiming that IPV (inactivated polio vaccine) was approved without proper safety testing, uses risky production methods involving monkey kidney cells, doesn’t stop the spread of polio, and that the FDA failed to ensure its safety before approval.

Several of Siri’s claims rely on package insert data, as opposed to actual clinical trial information. Vaccine inserts are legal documents and not medical or research documents. He repeats the oft recited claim that vaccines have only been tested for a short time without seeming to understand that the insert does not contain all the results of clinical trials, only what is required by regulations.

Vero cells, first developed in 1962, are one of the most common continuous cell line used to make vaccines. Siri claims that the “cells are susceptible to infection by dozens of viruses,” which is true, but that’s what makes them useful. These cells can be infected by many different viruses, which is why they are so useful for producing vaccines like those for rabies, flu, and yellow fever.

During the vaccine-making process, the cells are carefully cleaned and tested to make sure no harmful viruses end up in the vaccine. After weakening a virus in them, that virus is removed from the cell line. Vero cells are not cancerous, and they are not an ingredient in the vaccines themselves.

One of Siri’s other complaints is that IPOL, an inactivated polio vaccine (IPV), does not stop transmission of the virus. IPOL does not prevent the virus from infecting the intestines the way the oral polio vaccine (OPV) does. Because polio is spread through an oral-fecal route, a person vaccinated with IPV will not get sick with polio, but can pass it through their intestines to others.

However, IPOL does greatly reduce the amount of virus in the throat (called pharyngeal virus shedding). This helps lower the chances of spreading the virus to others. Unlike OPV, IPOL does not carry the risk of causing vaccine-associated paralytic poliomyelitis (VAPP), a rare condition linked to the oral vaccine.

Additionally, IPV has been proven effective in populations like in the U.S. and in much of the world, where poliovirus has been eliminated.